WASHINGTON (WUSA9) -- Jonathan Fullard has been sentenced to 25 years in prison for sexually assaulting and killing a toddler, the U.S. District Attorney said in a release on Friday.

According to court documents, 29-year-old Faullard was babysitting his former girlfriend's 20-month-old son, Keyontae Osbia Moore, at the 3000 block of 30th St. Southeast while she went to work on March 4.

The next morning he called this then girlfriend to tell her the toddler stopped breathing. The child was taken to United Medical Center in extremely critical condition, the release said.

The boy was then transferred to Children's National Medical Center, where it was determined he had trauma to his head and body. The boy died due to his injures on March 5, the release stated.

Evidence later suggested the toddler was sexually assaulted, the release stated.

In October 2012, Fullard pleaded guilty to second-degree murder for the death of the toddler.

He will be placed on five years supervised release after he serves his sentence and will be registered as a sex offender for the rest of his life, the statement said.